Attenuating vacuum tube voltmeter



June 9, 1953 D, GUREvlCs 2,641,626

ATTENUATING VACUUM TUBE VOLTMETER Filed Sept. 4, 1948 v 2 Sheets-Sheet l r N N INVENTOR.v

June 9,'1953 D. GuREvlcs 2,641,625

ATTENUATING VACUUM TUBE VULTMETER Filed sept. 4, 1948 2 sheets-sheet 2 0A W0 Gz//PEz//cs INVENTOR.

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Patented June 9, 1953 UNITEDfs'm-TES PATENT oFFicE ATTENUATING VACUUM TUBE VOLTMETER David Gurevics,lNew York, N. Y... assignortd.

Freed Transformer,.Company,r1nc., a corpora y tion o'flfevvyork?` `1 ApplicationsSeptember 4, 1948, Serial No. 47,781

L golaims.. (Cl. 171-.95l

Another object of the invention is an amplifier' of the inverted type includingone or more stages, parallel or series-connected, having an input lcircuit connected to the anode or.v another relatively high potential electrode, and an output circuit connected to the cathode or another relativelyv low potential electrode.

The amplifier may contain several stages connected in parallel or pushpull, or in cascade. In

the latterY case, the cathode or'output circuit of the rst stage maybe connected to the anode orl input circuit of the :second stage; 1n this way, any desired amount of input'en'ergy, otherwise unmanageable because of its relatively 'high po tential, may be Vconverted into any amount of output energy which will be manageable because of its relatively lowpotential.

The amplier may have any desired amplification characteristic, straight, or curved, in accorde. ance with the desired characteristic of theoutput voltage.

Any sort of tube is usable; Triodes have been found practical. vespecially those generally-used for inverse amplification purposes.v However, the invention may also be applied 'to' other tubes, especially multi-grid tubes such as tetrodes or pentodes. n

In such cases, inputand output circuitsof the attenuator may not only VbeV applied to anode and cathode respectively', but also to auxiliary or equivalent electrodes connected to or coupled to anode or cathode.

'I'he remaining features of the attenuator amplifier may be more or less conventional.

The control grid should be maintainedat. a potential relatively close to, or slightly for eX- ample, about below the potential of the anode or an equivalent electrode of the amplifier.

A cathode bias has been found useful for determining the characteristic of inverse amplication of the attenuator. However, other biasing methods may equally well be used in connection With appropriate tubes and circuits.

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vIn order to protect'the anode circuit the anode or equivalent electrode may be grounded-A` over relatively -high resistance. The Vanode Aresistance for example may be higher and of` a=-differentf order of magnitude; say'l-OG times highenthan' the corresponding vgrounding or biasing resistance of the cathode circuit.

A speciiic object of the invention isfafvoltage metering circuit, especially .one ofthe electronicv` type, where an 'electronic attenuator is `used to f control a tube voltmeter; IThis permits' the eval uation of vvery high voltages vri-th'extremer ac-v curacy and over. avery broad frequency frange; without requiring any substantial change in Ytheistructure ofavailabletubevoltmeters. 'f i A still more specific objectfof .the inventionis avvoltage metering circuit-adapted to: measurethe relatively high-voltage' existing across a con-1.'-

denser connected in ser-ies; resonantcircuits of' relatively highfQ value such as may be caused'- by the insertion -of an-'iron core inducta-nce ori.

transformer. Heretoiore `the accurate ror direct determination of such high Q values-was ex tremely diicult'if not impossible due to the' high Voltage and practical infinite impedancefexisting across theterminals of the adjustable-'condenser used for bringingthevQ metering circuit-to reso-1 nance.

In accordance with the invention-anielectronic Y attenuator coupling the condenser-with an ap..

propriatestandardvoltmeter -suc-h-asan; ordinary tube meter will permit exactmeasuring'of they high voltage. #The Q value of a. coilzconnected. in series with thefcondenser andan oscillatorl may thus be derivedfrom the well known-for-v mula,-Q==Ec'on/E0Scf wherein -Ecoris the condenser voltage and Ease the oscillator voltage` Inthis way," with one and -the samejl simple linf-AY strument, extremelyhighQy values, upto several thousands, maybe determined for .practicallythe entire useful f-requencyrange.`

These `and other objects of` the `inventionwill be Afi-irther:` described in connection with-:the-jac-f companying drawingsinwhichr' electronic attenuator embodying the inventiong" Figure 4 shows an electronic attenuatorvwith a pair ofy tubes connected in pushpull.y

Figure 5 shows an electronic attenuator conl sisting of two attenuatng stages connected ink cascade. 1

Figure 6 shows an electronic attenuator employing a pentode; the screen grid being used as an input electrode.

In Figure 1, I is a high voltage input source coupled over condenser 2 to the anode 3 of a triode 4. The grid is connected to the positive terminal of a source 6 of high potential of the order of or less than the input voltage. Grid 5 is also coupled over a high capacity condenser 1 to ground or to the other terminal of source I. The cathode 8 is connected over a coupling condenser 9 to a load device I0, and also connected over a relatively low biasing resistance I. Anode 3 is also connected' over a relatively high resistance I2 to ground or to the other terminal of source I.

With a more or less conventional tube and circuit, an inverse amplification factor of about 1:100 may be obtained.

' In Figure 2, I3 is a variable condenser which may be part :of an otherwise well known Q metering or series resonant circuit (not shown). The voltage across the condenser which is to be measured may be relatively high, say of the order of 150 volts. Y One terminal of condenser I3 is connected over a coupling condenser I4 of about .01 microfarad to anode I5 of a triode I6 of the 6J5type. The other terminal of condenser I3 is grounded. Anode I5 is also grounded over a resistor I1 of about 100'megohms.' Grid I8 of triode I6 is connected over an appropriate kresistance I9 to the positive terminal of a direct current source 2li,k of say 150 volts. Grid I8 is lalso coupled over a condenser '2i of 8 microfarads to ground. Cathode 22 is biased by arresistance 23 and coupled over a condenser 24 of say 2 microfarads to the grid or input circuit 25 of av three stage amplifier including the three pentodesZB, 21 and 28. The output circuit of the last pentode 28 isV coupled over rectiers 29 to the input c ircuitl of amplifier stages 3E) which are Apart of la tube voltmeter 3l containing in its output circuit, as Vmeasuring instrument, the milliameter 32. Y

In Figure 3, two triodes 33, 34 have anodes 35, 36 connected in parallel to the common input oscillator` 31. The two grids 38, 39 are interconnected and connected (in a manner not shown) to-a common source of high potential. The cath-V odes 40, 4| are also interconnected and the common connection istaken over aresistance 42 to ground, and also in a manner notshown butl similar to that shown in Figure 1, to a common load circuit. f f 1 Figure 4 shows a pair of electronic attenuators embodying the-'invention and arranged in' mina]` of 'a source of' high D. C'. voltage. The e two'catliodes 48, 49 are connected in parallel'over separate'grounding4 resistors 50, 5I to ground;l the output ofthe attenuator is taken from terminals 52. 53.5

Figure 35 shows two attenuators arranged in cascade. The cathode output of one attenuator stage 54 is taken over a coupling condenser 55 Vto the anode of a second attenuator stage 56 from the cathode of which the output is derived in a manner already explained above. By cascading several stages, any amount of inverse amplication and any amount of attenuation may be obtained. f

Figure 6 shows an electronic attenuator consisting of a pentode with input and output circuits being applied to or taken oi at ESI-58, and 59, 6D, respectively. y,

' A screen grid tube may be used in similar arrangement except that the suppressor grid may be tied to the cathode. The pentode tube may also be replaced by a remote control cut-oi tube such as a variable u tube, without exceeding the scope of this invention.

What I claim is: p

1. In a voltage metering circuit adapted to measure a relatively highA. C. voltage across aV variable condenser connected in a series-resonant circuit of relatively high Q, a tube volt fmeter, a source of high D. C. potential, a vacuum tube arrangement including an' anode type electrode coupled` to saidy condenser, av cathode' type output electrode coupled to said tubev voltI meter; and a grid type electrode coupled to said D. C. source at the positive terminal thereof; the negative terminal being resistance cou-` pled to Vsaid anode type and'cathode type elec-l trodesrespectively. A

2. Device according to vclaim 1 wherein said vacuum tube arrangement consists of a triode comprising, aV high voltage A. C. input source capacity coupled to the anode of said triode, and a source vof high D. C. potential of the order of less than that of the input voltage and coupled' to the grid of the triode; the grid of said triode being also capacity coupled to ground and the cathode of said triode being capacity coupled to control said. tube volt meter; `a relatively low biasing resistance coupling the cathode to ground;

anda relatively high resistance coupling the anode' to ground. y

' DAVID` GUREVIC'S.

References Cited in the file of this patent Selinger Mar. 7, 1950 

